linux-kernel - Re: [PATCH 6/8] ARM: clang: Do not relay on lr register for stacktrace

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Message-Id: <20211015091832.3e114751496041931f214bab@kernel.org>
Date:   Fri, 15 Oct 2021 09:18:32 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     "Russell King (Oracle)" <linux@...linux.org.uk>
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        "Naveen N . Rao" <naveen.n.rao@...ux.vnet.ibm.com>,
        Ananth N Mavinakayanahalli <ananth@...ux.ibm.com>,
        Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
        Sven Schnelle <svens@...ux.ibm.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 6/8] ARM: clang: Do not relay on lr register for
 stacktrace

On Thu, 14 Oct 2021 17:53:24 +0100
"Russell King (Oracle)" <linux@...linux.org.uk> wrote:

> On Fri, Oct 08, 2021 at 09:29:08PM +0900, Masami Hiramatsu wrote:
> > Currently the stacktrace on clang compiled arm kernel uses the 'lr'
> > register to find the first frame address from pt_regs. However, that
> > is wrong after calling another function, because the 'lr' register
> > is used by 'bl' instruction and never be recovered.
> > 
> > As same as gcc arm kernel, directly use the frame pointer (x11) of
> > the pt_regs to find the first frame address.
> 
> Can I ask that the subject line is corrected. It's "rely" not "relay".

Oops, yes, that's my typo. Thanks for correcting!

> 
> Also, the frame pointer is called "r11" not "x11" if you want to use
> the numerical register reference for 32-bit ARM registers.

Oh, I mixed up the register name between arm64 and ARM...

Thank you,

> 
> Thanks.
> 
> -- 
> RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
> FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!


-- 
Masami Hiramatsu <mhiramat@...nel.org>